Usage of ultraviolet sterilizers in developed countries
At present, more than 3,000 drinking water facilities in Europe are disinfected by ultraviolet rays, and the larger ones are Rotterdam Water Plant in the Netherlands (470,000 m3/d), St. Petersburg Water Plant in Russia (860,000 m3/d) and Styrum-Ost Water Plant in Germany (192,000 m3/d). In North America, due to the strict regulations on cryptosporidium, Giardia and disinfection by-products in the new drinking water standard, ultraviolet technology has received unprecedented attention. The Environmental Protection Agency (EPA) of the United States quickly established the application standard of ultraviolet technology in drinking water treatment after research proved that ultraviolet is the most effective and feasible technology to control cryptosporidium and Giardia. According to the second-stage enhanced surface water treatment regulation (LT2ESWTR) issued by the United States in 2006, in the process of drinking water treatment, 3 logs of Giardia, 4 logs of virus and 4 logs of Cryptosporidium must be removed or inactivated. Because chlorine disinfection has little effect on cryptosporidium, LT2ESWTR requires existing waterworks to adopt filtration plus ultraviolet or ozone disinfection process, while new waterworks need to adopt filtration and multi-stage combined disinfection process. At present, the large-scale water supply plants in North America are Chicago Zhonghu Water Plant (1.8 million m3/d), Seattle Water Plant (680,000 m3/d), Vancouver Victoria Water Plant (5 1.0 million m3/d) and Montreal Water Plant (3 million m3/d). The aforementioned Waterworks in Walkton, Ontario, Canada, also adopted ultraviolet disinfection technology after the incident of pathogenic microorganism infection in 2000. The UV disinfection system for tap water in new york, USA, which is under construction, has a processing capacity of 8.36 million m3/d and is the largest UV disinfection project for drinking water in the world. According to statistics, in 2000, large and medium-sized waterworks in the United States did not use ultraviolet disinfection system, but by 2006, the proportion of large and medium-sized waterworks that used ultraviolet disinfection rose to 10%. In recent years, more ultraviolet projects are under construction or have been put into use. The application of ultraviolet technology in drinking water disinfection represents the development trend of disinfection technology in the world at present.
Application of ultraviolet sterilizer in China
The first urban water supply plant in China is Daqing Dongfeng Water Plant (50,000 m3/d). The system was originally disinfected by chlorine dioxide. In order to reduce the operation cost, a household ultraviolet disinfection system was adopted. However, the system lacks the feasibility of the previous process and the subsequent application research, so it fails to provide valuable data. Since 2004, Tsinghua University and his cooperative team have systematically studied the ultraviolet disinfection technology of drinking water. In 2005, a pilot-scale ultraviolet disinfection system (500 ~ 600 m3/d) was established in Dongguan, Guangdong, and it has been running ever since. A pilot study of 100m3/d was carried out in Beijing No.9 Water Plant on October 20, 2007. On the basis of full investigation, the third-phase ultraviolet disinfection project (654.38+500,000 m3/d) of Tianjin Development Zone Water Purification Plant was completed in July 2009. This water plant is the first water purification plant designed and put into operation simultaneously with ultraviolet disinfection and main process in China. At the same time, in order to ensure the water supply safety of the World Expo, an ultraviolet disinfection system (600,000 m3/d) was added during the renovation of Shanghai Linjiang Waterworks.